What is the scope of lens in saltStack?

I am working on Salt related stuffs, here I found **lens** inside the augeas module.I have been looked into the saltStack documentation but I could not able to figure out what it actually does ? augeas.change: - context: /files/etc/redis/redis.conf - lens: redis.lns - changes: - set bind 0.0.0.0 - set maxmemory 1G Here in above rule my understanding is look for the file redis.conf and set the bind parameter to 0.0.0.0. But my question is what **lens: redis.lns** will do here ? Your help will be appreciated.